Two-motion type automatic telephone switch arranged for testing two or more lines ofa selected group simultaneously



Aprll 18, 1950 R. TAYLOR EI'AL 2,504,755

TWO-MOTION TYPE AUTOMATIC TELEPHONE SWITCH ARRANGED FOR TESTING TWO ORMORE LINES OF A SELECTED GROUP SIMULTANEOUSLY Filed Feb. 14, 1946 2Sheets-Sheet 1 T INVENTOR.

- REGINALD TAYLOR GEORGE THOMAS BAKER ATTORNEY i 18, 1950 R. TAYLOR ETALTWO-MOTION TYPE AUTOMATIC TELEPHONE SWITCH ARRANGED FOR TESTING TWOOR'MORE LINES OF A SELECTED GRQUP SIMULTANEOUSLY 2 Sheets-Sheet 2 FiledFeb. 14, 1946 F I G. 2

00 0 0 0 0 0 0 0 0 00% 0 0 09 0 9 P II 000 m 090 2 O0 %0 +2 000 00 P2 00J l O 0 ll 0 i m H 5 6 E v 5 v w r R H M N N m H 4 H v 2 N 7 l 4 A/ B HJ w 4|? 4 w 5 2 w R Y m R X j 6 B N N C H m m a I. 1 1 IT w w I H T O Om w 7 7 INVENTOR. REGINALD TAYLOR Patented Apr. 18, 1950 UNITED smartsATENT OFFICE TWO-MOTEON TYPE AUTOMATIC TELE- PHONE SWITCH ARRANGED FORTESTING TWO OR MORE LINES OF A. SELECTED Git/0UP SIMULTANEOUSLY tion ofDelaware Application February 14, 1946, Serial No. 647,598 In GreatBritain March '7, 1945 7 Claims.

The present invention relates to automatic switches for use in telephoneor like systems and is more particularly concerned with switchesarranged to perform a hunting operation to test for a line marked in aparticular manner. The invention moreover is particularly applicable togroup selector switches of the well known vertical and rotary type,especially those equipped with two sets of wipers so that testing takesplace over two lines simultaneously. v

A switch of this general type is disclosed in United States Patent No.2,137,423, granted November 22, 1938, to Reginald Taylor and GeorgeThomas Baker, and one of the special features is that when a free lineis encountered and seized by a switch which is hunting over a group, themarking of the line as busy is effected very rapidly in order to reducethe chances of two switches seizing the same line. For this purpose useis made of a relay which is maintained operated by busy potentialencountered by the test wiper during its movement and which releases toapply busy potential when an idle outlet is reached. With the need forincrease in the speed of hunting switches, it is sometimes found thatthe wipers tend to overshoot the contacts momentarily and if thisoccurs, the maintaining circuit for the relay is opened and it maytherefore release and cause the switch to seize a busy line. The chiefobject of the invention is to provide improved arrangements whereby ifsuch overshooting action should occur it will not prejudice theoperation of the switch and hence the danger of double connections iseliminated.

According to one feature of the invention, in an automatic switcharranged to perform a hunting operation under the control of a relaywhich is maintained energised as long as marked lines are encounteredand when energised closes a point in a self-interrupted circuit for thedriving magnet, the relay is adapted to be held operated over onewinding in series with the driving magnet until the magnet operates itsinterrupter contacts and thereafter to be maintained over a secondwinding by potential picked up by a test wiper if a marked line, is thenencountered.

According to another feature of the invention, in an automatic switch ofthe vertical and rotary type arranged to be set by impulses in thevertical direction and thereafter to perform a hunting operation in therotary direction under the control of a relay which is maintainedenergised as long as marked lines are encountered and when energisedcloses a point in a self-interrupted circuit for the driving magnet, afurther relay which is energised as soon as the switch is taken into.use is arranged to be intermittently short-circuited in a circuitincluding operated contacts of the hunting control relay while impulsesare being received and on de-energisation by prolonged short-circuitingwhen the impulses terminate serves to initiate the hunting operation.

The invention will be better understood from the following descriptionof a preferred method of carrying it into eifect which should be takenin conjunction with the accompanying drawings comprising Figures 1 and2. These drawings are diagrammatic in form and when arranged side byside show the circuit of a ZOO-point group selector of the vertical androtary type arranged to have so-called rectangular release, that is tosay the wipers are restored to normal by continuing their rotarymovement until they are clear of the contacts after which they fall. androtate back to normal beneath the bank. I Considering now the operationof the switch in detail, when it is taken into use, relay A is operatedover the loop by way of itsouter windings and thereupon completes acircuit for relay B from earth over contacts N3 in serieswith resistorYB and vertical magnet VM. Magnet VM is inoperative in this circuit butrelay B operates and at contacts Bl completes a locking circuit foritself, at contacts B2 energises relay C in series with rotary magnet RMwhich is inoperative in these circumstances, at contacts B3 earths theincoming P conductor to hold the preceding switches if necessary, atcontacts B4 prepares acircuit for relay I-IB, at contacts B5 connects upthe middle winding of relay A and at contacts B6 opens a point in therelease circuit which extends to earth by way of suitable delayed alarmequipment over common lead l3.

It may be mentioned that the switch is equally suitable for use as afirst group selector, an incoming selector or a subsequent groupselector. If it is being used as a first selector, the middle winding ofrelay A is now connected to dial tone by way of cam contacts SI andcommon lead l0 and the relay in known manner serves as a tonetransformer so that dial tone is audible to the calling party. If the"switch is notbeing used asa first selector, the connection to lead 10isnot made. Moreover, if the switch is being used as a first selectorterminals It and i5 may be strapped so that an immediate guard on the Pconductor is provided by contacts Al over ofi-normal contacts N4 in themanner described in United States Patent No. 2,424,519 granted July 22,1947, to Reginald Taylor and ueorge Thomas Baker.

- will engage busy. lines.

' Relay 0 upon operating, at contacts C I short circuit for magnet VMwhich therefore operates to raise the wipers a correspondingnumber ofsteps. Relay B is short-circuited intermittently but not sufiicientlylong tocause itsv release; As soon as the switch moves off-normal, the

vertical off-normal contacts are operated and at contacts N l a point isclosed in the rotary magnet circuit, at contacts N2 circuitsarecompleted for relays HA and HB over contacts NR5 and NR4respectively, at contacts N3 the initial circuit .efrelayBis opened andat contacts N4 the connection of relay B. to the]? .conductorisinterrupted to prevent. this. relay being. .he1d..up subsequently, Relay.HA at. contacts HA! closes another point .inlthe rotary magnet.circuit, at contacts. HA2 prepares. a lockingcircuit-for itself toathe.test. wiper P2,. at contacts. HA3. and HA5 connects up. the. wipers l'and +l,.at contacts HA4. completesan alternative circuit for relayC, atcontacts :I-IAQpreparesashunting circuit for relay. C. andatcontactsHAlprepares a holding circuit for relay HR to the. test wiper Pl RelayHB-performs .somewhatsimilar functions and particularly. at contacts HBlconnects relay HA .towiper' P2, at. contacts. H132; connects itself towiper Pl,..at-.contacts HES and HBEconnects up ..wipers -.-.2.:and.+2,.at. contactsI-IB4 completes an..al1ternative circuit for relay .0,.at contacts H136 .changes over. the. subsequent operating. circu'itsforitself and relay I-IA,-at.contacts;I-IB1 .closesanotherpointin theshunting circuit for relay 0., and at contactI-IB8 .closeslanother pointin therotarymagnet circuit.

. 'In viewofthecircuit .completed..over contacts A! ..HAB; H81 .and. C2,relay ,0. is...intermit,- tently-short-circuited during thetrainof im- 4Consider first the case in which wiper Pl encounters an idle line whilewiper P2 encounters a busy line. Since wiperPl. does not pick up earth,no circuit is provided. for. maintaining relay EB and it thereforede-e'nergises, thereupon at contacts BB3 opening a further point in therotary. magnet circuit and at contacts HBl disconnecting relay HAfromwiper P2 so that this relay also de-energises.

Relays HA and HB are shunted respectively by resistors YF and YE theresistance value of which is so chosen as to give pulses but remainsenergised. ..Atthe. end of the train, however, relayA remains steadilyoperated and relay Ctherefore releases, ..thereuponat contacts C4completing the rotarymagnet circuitin series .withthe low. resistancewindings of relays HAandHBL. The magnet therefore operates. toadvanceathe .wipersinto engagement with .the first; set. ofbankcontactsand. at theend of its stroke opens. the. interrupter.c0ntacts RMC whereupon itQis de-energised. .On the first. ro- .tarystep the rotaryofi-normal contactsiare operated, thereuponat contactsNEH-ensuring that resistor 23 remains .includedlin .the. verticalmagnet. 'circu'it,.at contacts NR2 and NR3 preparing or -the.disconnection of. relay A and at. contacts and N35. opening. the initialcircuits. of relaysHB and HA. ..Jn yiewofthe factthat the circuitsiover.thelow resistance windings. of relays H'AandHB havelbeenvopened.andsalso that. the

initial circuits ..overhtheihi hi resistance .vvindingsv ane-(longer..ayailahle, these. relays ..are ..now dependent for their. continued.operation. on earth picked up byzwinersPtand. P2. 1. Eour possibilitiesmay now .arise, viz. that wiper?! .vdllengage an idleline .whilewiper P2will engage. abusyline, that both wipers engage idlelines, that wiper P2will engage-1am idle line-and wiper Plarbusy one; or that both wipersicase of possible overshoot of the wipers.

.the required release lag to cover any momentary interruption of themaintaining circuits in the The release .of-relay HB applies animmediate guarding earth to wiper Z PI over contacts S2 and B4 so as toseize the free outlet engaged by this wiper.

"Moreover, at contacts HB! the short-circuit completed around relay C atcontact C2 is removed and relay C therefore reoperates. .Thereupon a newcircuit is completed. for relay HA over contacts B3,. Nzland C5,.resistor. YD. and contacts Relays C andI-IAjthen connectup thef firstset of tallcingwipers-sl and I. and the incomlog P conductor. isconnectedithrough to wiper over c'mtactsQHBZ', S2 .and'HA'l. .Relay HAalso completes -a. holding. circuit. over contacts andC2 for relay. C.1.The operationof relay (3 disconnects relayAlfrom the line, whereuponit releases and short-circuits relay B-and transmitsapnlse to themagn'etwhich ishowever ineiiective. owing to ,the inclusion of. resistor YB in.the circuit. .RelaylBjde-energises after its siowpericd. and removes thelocal guarding. earth from the P conductor at contacts 33, opensitheiniti'al.;circuitof reIayICat contacts B2 and prepares; the releasecircuit. at contacts IE6; Relay Harrow remaihsenergisdfrom earth on the?conductor and relay ..C. is maintained dependent upon relayHA.

. j If bothoutlets.encountered are. idle, .neither relay HA nor relay.HB can be held up. over the V In the third case .in which wiper PIencounters earth andwiper Pz Idoes not relay HAisdeenergised andrelay'HB..remains. operatedowing ,tqfthe fact that contacts HAT. are shuntedby contact B4. The release vof relay .HA, however, removes theshort-circuit fromrelayC-and this relay operates with the resultspreviously described. It will be appreciated. that. anlimm'ediateguard'is provided, on wiperP2 over contacts HB! and. HA2 andjthatduringthesubsequent connection, r'elayl-I-B-is .held .up over. contacts.HBL HAL'NZ and C5,.resistor. YDand contacts a 1156.. The. second.sets-of. .talln'ng wipers '-2 and +2 are accordingly connected ..up. atcontacts HB3.and 'HB5oover res.ting...contacts HA3 and L HA5 and.v relay1021's. maintained...eneraisedover In! the; 'fourth..c'ase..in-.whicheboth wipers. .encounter busyoutlets,.. .both. relays: HA:-andrema'inenergiSed. andconsequently whenthe interrupter.contactsfRMC...again close, the-magnet RM...is re-.energised..and.advances the wipersa turtherstep. ..In;lthe positionz then reachedJall tour;possibilitieseaare,againoperative. ..It may be-';pointed-:outthatxthe. speed.-of-. rotary stepping maywbe-waccurately:controlled:by:theshunt pro.-

vided by resistor YA and the'leak comprised by resistor YC.

If the wipers are advanced over the whole group without either wiperencountering a free line, the eleventh step position is reached in whichthe so-called cam springs S are operated. Thereupon at contacts S2 anoverflow meter connected to lead I6 is operated over the 11th stepposition of wiper PI and the holding circuit for.

relay HB is opened. It accordingly releases and opens the circuit ofrelay HA which would be released in any event since the 11th stepcontact in the bank of wiper P2 is unwired. Thereupon relay C isre-operated and again brings up relay HA whereupon conditions similar toswitching on the first set of wipers are established except that thenegative and positive wipers are now connected back to .the outerwindings of relay A over the eleventh step positions of wipers 1 and +1.At contacts Si busy tone earth over common lead I I is connected to themiddle winding of relay A and at contacts S3 earth and battery appliedalternately to common lead l2 are connected to the middle and lowerwindings of relay A. This relay again acts as a tone transformer forrepeating the busy tone and during the flash or battery periods therelay is maintained over its middle winding and leads II and When thecalling party hangs up in response to the receipt of busy tone, relay Ais released during one of the earth periods on lead [2 and thereuponshort-circuits relay B. This relay on releasing removes earth from the Pconductor at contacts B3 whereupon relay HA is released and in turnopens the circuit of relay C. When relay C also is released the circuitof the magnet RM is again completed at contacts C4, this time to therelease alarm earth over common lead l3 and contacts B6. The wiperstherefore take a fur- I ther step, fall, and rotate back to normalbeneath the banks, the vertical and rotary offnormal contacts then beingrestored. During the release time of relay C the P conductor ismomentarily unguarded so as to permit the release of preceding switches.Earth is then replaced on this conductor at contacts C5 until the switchhas restored to normal and contacts N2 open. It will be noted, however,that even if the switch should be seized during the unguard period, re-

lease cannot be interfered with since no circuit can be completed forrelay B until full restoration has taken place.

The return of the switch wipers to normal after an ordinary successfulconnection takes place in generally similar manner when earth is removedfrom wiper Pl or wiper P2 as the case may be to permit the release ofrelay HA or relay HB. 'Ihereupon relay C is released and the restoringcircuit for the switch is completed.

If the switch is released Without any impulses having been transmittedthereto, the conditions are slightly different. In this case relays A, Band C are all energised when the loop is opened and a single impulse istransmitted to the magnet VM which therefore raises the wipers to thefirst level and operates the off-normal contacts so that relays HA and,HB are energised. On the sub sequent release of relay B, however, thecircuit for relays HA and HE is opened at contacts B3 and these relaystherefore release and bring down relay C whereupon the wipers arerestored to normal in the usual manner.

It will be appreciated that since relay C has only one winding and isenergised as soon as the switch is taken into use, the circuitconditions" governing its release are the sameat whatever stage thecalling party hangs up. This ensuresa uniform release time for relay Cand hence an unguard period of constant length, which sim-,- plifies themaintenance required for securing ellicient operation of the system.

We claim: V

1. In a telephone system, a switch having a test wiper, a test relayhaving two windings, a stepping magnet, interrupter springs operative bysaid magnet, a circuit including said springs, said magnet and onewinding of said relay in series with said magnet, means for operatingsaid relay over said second winding, means responsive to said operationof said relay for causing said circuit to operate said magnet thereby tostep said;

wiper in a hunting operation, said last means alsoretaining said relayin said operated position over said one winding in series with saidmagnet until said magnet operates said springs, means for disabling saidfirst means, a second circuit including test contacts, said wiper andsaid second winding for maintaining said relay in said operated positionwhe said wiper encounters marked test contacts, an operation of saidsprings by said Wiper disabling said one Winding, said relay thereaftermaintained in said operated position over said second Winding inresponse to said Wiper successively engaging marked test contacts.

2. In a telephone system as claimed in claim 1 together with a resistiveelement in shunt of said second winding, means for causin the release ofsaid operated relay, said resistive element in shunt of said secondwinding providing a controlled release lag for said operated relay.

3. In a telephone system, a switch having a test wiper, a test relay, astepping magnet, interrupter springs operative by said magnet, a circuitincluding said springs, said magnet and said relay in series with saidmagnet, a second circuit, means for operating said relay over saidsecond circuit, means responsive to said operation of said relay forcausing said first circuit to operate said magnet thereby to step saidwiper in a hunting operation, said last means also retaining said relayin said operated position in series with said magnet until said magnetoperates said springs, means for disabling said second circuit, a thirdcircuit including test contacts, said wiper and said relay formaintaining said relay in said operated position when said wiperencounters marked test contacts, an operation of said springs by saidmagnet disabling said first circuit and disconnecting said relay from inseries with said magnet, said relay thereafter maintained in saidoperated position over said third circuit in response to said wipersuccessively engaging marked test contacts.

4. In a telephone system as claimed in claim 3 together with means fordisabling said third circuit to cause the release of said operatedrelay, and means for controlling the release time of said operated relaythereby to delay the releasing of said operated relay.

5. In a telephone system, a switch having a relay, a wiper and astepping magnet, a normally incomplete self -interrupting circuit forsaid magnet, means responsive to a seizure of said switch for causingsaid relay to operate, means responsive to a series of impulses receivedafter said seizure for intermittently completing a short circuit aroundsaid relay While said relay is maintained in said operated position,said last means maintaining said short circuit for a prolonged intervalwhen said series of impulses ceases thererelay for 'cbmpl'e'tirig said'seIf -interruptin circmt trisreby to cause "said magnet to step saidwiper.

'61 I'n a tle'phbfie a-switch having a plurality of test wipersg apliiralityof test relays each having two windings, a steppi'ng -magnet,imr-rupter spi ihgs ope'raiti ve 'fiy' said" magnet,- a eirombineludings'a id spx 3 said magnetand;

ther and'with saidmagri t;'mans--foi** causing e'i atiiisaid 'm'efan's'also- 'energizin' r said ielays over said one Wihdi-ngs' in srie'switheach. other and with said magma-until said magnet operates said:springs, aiplfira'lity 9f 'other sir cuits' ficl'i including i651?"Eonfiact'S, 6119'- of s aid 'wip'e'fs V and "one of safd seso'nd' windings for'maintain ing: one-0f said relays" n'er'gizd when said onewiper encounters-marked: tes't" eondjac'qs; anopefaticn of said s ringsby said magnet 'dis'a'bIingsaici t me 7 means for disalilin windings,eachs'aiii' relay there'aziter main vained said respective wiperSiil'zssively engaging marked test contacts.

7 .-I'n" a te1eph0ne System, aswitch having "a test reI-ay, tiesfl(idncacts', a test wiper,- a sfieppin'g magnet; aseIf -interruptifigcir'cuit including said relay in series with said magnet, acontrol-relay,

testirelay in response on said r'e-operation 0:75am? cti'ntrol relay.

GEORGE THOMASBAKER.

EEFERENCES 011 11 The fb l'lbwin'g' rfer' uses are of res-9min the file'of his @aten-t: f

UNITED STATES PATENTS Numbar Name Date;

15,623,230 Bellamy r Apr. 5,192? 1,696,254 Pine'll ..;Dec. 25, 19281,725,152 Lomax; AugF ZO; 1929 1,868,296 Stokely July 19, 1932 2,137,423Tay10lf m NOV; 22,1938

